1. Field of the Invention
The present invention relates generally to personal audio devices such as headphones that include adaptive noise cancellation (ANC), and, more specifically, to architectural features of an ANC system in which performance of the ANC system is measured and used to adjust operation.
2. Background of the Invention
Wireless telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as MP3 players, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing adaptive noise canceling (ANC) using a reference microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events.
However, performance of the ANC system in such devices is difficult to monitor. Since the ANC system may not always be adapting, if the position of the device with respect to the user's ear changes, the ANC system may actually increase the ambient noise heard by the user.
Therefore, it would be desirable to provide a personal audio device, including a wireless telephone that implements adaptive noise cancellation and can monitor performance to improve cancellation of ambient sounds.